Antennas and antenna systems are utilized with radio frequency transmission and reception devices for communications and control. An antenna system is the combination of the electromagnetic radiation elements of an antenna, the feedline, the matching networks, the impedance circuitry, and the physical structure of an interface between electromagnetic space fields and the radio frequency input/output port of a radio frequency transmitter or receiver device. Different types of antenna systems are valuable for certain applications which require specific physical and electrical characteristics. The bandwidth and impedance match of an antenna system is very important for both broadband and narrowband signals used by devices for communications and control in the electromagnetic spectrum. Many electronic radio frequency devices which utilize antennas require that the impedance of the antenna system closely matches the impedance of the radio frequency device circuits. In previously known conventional dipole and monopole antenna systems, resonant wires and conductive bars or plates are used as radiating elements. Added matching circuits in the radio frequency device circuitry or at the junction of the feedline and antenna element feedpoint of the system are utilized in an effort to match the impedance and resonance to that required by the radio frequency device so that useful electronic signals may be conveyed efficiently. The evolution of predominant spectrum use from narrowband to broadband radio frequency communication devices requires new antenna system characteristics. For best performance, an antenna system should provide a good impedance match and electromagnetic radiation efficiency within the desired broadband part of the spectrum, and it may be desirable to reject other bands of non-interest.
Disclosure of the Invention
Description of the Invention and the Preferred Embodiment of the Invention